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Sidewinding snake-bot slithers over sandy surfaces

By Aviva Rutkin

(Image&colon; Henry Astley)

Watch out, desert-dwellers&colon; this snakelike robot can slither its way sideways up a sand dune.

Snake-shaped bots could one day scout archaeological sites, repair hard-to-reach devices and rescue disaster victims. But though the machines can wriggle their way into smaller and tighter spots than their legged counterparts, there are still some movements they haven’t quite mastered. Take sidewinding&colon; an unusual sidelong motion that lets some real snakes climb up steep and slippery surfaces.

“Sidewinding appears to be a really complicated and an unintuitive way to move on sand, and no one knew in any detail why it’s so good or why they do it,” says Daniel Goldman, a physicist at the Georgia Institute of Technology in Atlanta. “It allows the animals to do pretty extraordinary things.”

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Sidewinder secrets

To figure out biology’s trick, Goldman and colleagues observed six sidewinder rattlesnakes (Crotalus cerastes)at Zoo Atlanta as they made their way up sandy slopes at different inclines. It turned out that, as the slope of the hill became steeper, the sidewinders would keep more of their body in contact with the sand. This kept the ground beneath their body steady and allowed them to push their way up the hill.

The team used their observations to program the snake robot, developed by Carnegie Mellon University in Pittsburgh, to move its body in the same way. Now, the bot can sidewind up dunes with a 20-degree incline. Any steeper, and the sand becomes unstable and much more difficult for any snakes – real or robotic – to navigate.

Next up, the team is toying with different ways to make the bot’s body undulate vertically as well as horizontally. “It turns out you can make the robot ridiculously manoeuvrable,” says Goldman. “This paper is the tip of the sand dune.”